The present invention relates to a fixing device for improving the flatness of sheets of paper or similar information supports carrying a toner developed image fixed through the fixing device and for eliminating the spontaneous curling of sheets discharged therefrom.
In conventional copying machines a-straight heating element is arranged perpendicularly to the forwarding direction of the sheets of paper or information supports and is fixed on a heat refractory support. A belt-type transport element is positioned between the heating element and the face of the sheet of paper or information support on which a toner powder image has been deposited and a pressure roll is pressed against the back of the information support. The heat and pressure fix the toner powder image to the sheet of paper or information support.
In such copying machines the sheets tend to curl as they emerge from the fixing device as a result of the application of the heat to one face of the sheet.
Devices for eliminating the curling of paper sheets emerging from a fixing unit in a copying machine are well known. In particular our European Patent Application Number EP-A No. 0485123 discloses that forwarding rolls may be positioned downstream of the fixing unit. These rolls pull the sheet in the opposite direction to the preferred direction of curling of the sheet as it emerges from the fixing unit. This device is, however, large and expensive owing to the large number of components required.